1. Field of Invention
The present invention relates to a hydraulic controller for an automatic transmission mounted on a vehicle or the like, and more particularly to a hydraulic controller capable of fixing a control valve utilizing a switching valve when a hydraulic pressure output from the control valve is not used.
2. Description of Related Art
FIG. 3 shows a hydraulic circuit of a conventional hydraulic controller 100 for an automatic transmission, and FIG. 4 is a schematic diagram showing a part of the hydraulic circuit shown in FIG. 3.
In FIG. 3, reference numeral 87 denotes an oil temperature sensor and reference numeral 89 denotes a pressure sensor.
A linear solenoid valve SLT outputs a signal pressure (SLT pressure) Pslt, based on a throttle opening or the like, to oil passages a1, a2. A clutch modulator valve 76 adjusts a line pressure PL from a hydraulic pressure generating source (not shown) and outputs it as a range pressure (clutch modulator pressure) Pcmod to oil passages c2, c3 and c5 through oil passages c1, c4 and a strainer 85. A solenoid modulator valve 83 reduces the range pressure of the oil passage c5 by a predetermined amount and outputs it as a solenoid modulator pressure to oil passages g1, g2 and solenoid valves SOL, SOL2. A secondary sheave control valve 73 adjusts the line pressure PL to a secondary sheave pressure and outputs it to a hydraulic actuator for a secondary sheave 35 of a continuously variable transmission mechanism, based on the solenoid modulator pressure from the oil passage g2 and the SLT pressure Pslt from the oil passage a1.
Also, as shown in FIGS. 3 and 4, a garage shift control valve 77 adjusts the range pressure from an oil passage c4, based on the SLT pressure Pslt from the oil passage a2, to provide a direct control pressure through an oil passage k1 for directly controlling the engagement state of a clutch C1 or a brake B1. A garage shift valve 79 switches between the range pressure Pcmod from the oil passage c2 and direct control pressure from the oil passage k1, based on the signal pressures Psol1, Psol2 of the solenoid valves SOL, SOL2, for output to the oil passage 1. A manual shift valve 75 which is moved by operation of a shift lever (not shown) and outputs the range pressure or the direct control pressure of the oil passage 1 to a hydraulic servo 30 of the clutch C1 through an oil passage d in drive (D range) and to a hydraulic servo 31 of the brake B1 through an oil passage e in reverse (R range).
A feedback pressure is input through the oil passage k2, while the direct control pressure is output to the oil passage k1 from the garage shift control valve 77, counter to the SLT pressure Pslt from the oil passage a2 in the valve 77, to provide feedback control of the direct control pressure. The feedback pressure is input into a clutch modulator valve 76, a solenoid modulator valve 83 and a secondary sheave control valve 73, as well as the garage shift control valve 77.
In the above hydraulic controller 100, a shift lever (not shown) may be positioned so that direct control pressure from the garage shift control valve 77 is supplied to a hydraulic servo 30 of the clutch C1 or to a hydraulic servo 31 of the brake B1 through a garage shift valve 79, to control the engagement state of the clutch C1 or the brake B1. When the vehicle starts to run, the garage shift valve 79 is switched to supply a range pressure Pcmod from the clutch modulator valve 76 to the hydraulic servo 30 of the clutch C1 or to the hydraulic servo 31 of the brake B1, to bring the clutch C1 or the brake B1 into a completely engaged state.
However, as shown in FIG. 3, even when the range pressure Pcmod of the clutch modulator valve 76 is supplied to the clutch C1 or the brake B1, the garage shift control valve 77 is simultaneously controlled by the linear solenoid valve SLT through an oil passage a2, since the linear solenoid valve SLT controls the secondary sheave control valve 73 and a secondary sheave 35 of a continuously variable transmission mechanism. During such control the range pressure Pcmod supplied from the clutch modulator valve 76 through an oil passage c4 is repeatedly adjusted based on the SLT pressure of the linear solenoid valve SLT, output to an oil passage k1, feedback-controlled through an oil passage k2, and drained from the drain port EX to a low hydraulic pressure.
Even though output of the garage shift control valve 77 is shut off by the garage shift valve 79, and pressure adjustment of the garage shift control valve 77 is not required, oil supplied from an oil pump (not shown) through the clutch modulator valve 76 and the oil passage c4 is unnecessarily drained to the drain port EX, which increases oil consumption in the hydraulic controller 100, and results in reduction of fuel economy due to upsizing of the oil pump or decreased efficiency of the oil pump.
The present invention provides a hydraulic controller for an automatic transmission which feedback-controls a first control valve through an oil passage when a switching valve outputs a hydraulic pressure output from the first control valve, and fixes the first control valve through that same oil passage when the switching valve outputs a hydraulic pressure of a hydraulic pressure generating source.
More specifically, the present invention provides a hydraulic controller for an automatic transmission which includes a hydraulic pressure generating source which outputs a first hydraulic pressure, a solenoid valve which outputs a signal pressure, a first control valve, and a switching valve. The first control valve includes a first oil chamber and a second oil chamber, arranged opposed to the first oil chamber. The signal pressure of the solenoid valve is received into the first oil chamber, and the first control valve adjusts the first hydraulic pressure of the hydraulic pressure generating source, in accordance with the signal pressure, and outputs the adjusted pressure as a second hydraulic pressure.
The switching valve receives the first and second hydraulic pressures and switches between and outputs one of these received hydraulic pressures, with the output of the switching valve passing through an oil passage into the second oil chamber of the first control valve.
When the switching valve outputs the second hydraulic pressure from the first control valve, the hydraulic controller utilizes that second (adjusted) hydraulic pressure for feedback control by supplying it to the second oil chamber of the first control valve. On the other hand, when the switching valve outputs the first hydraulic pressure (for example, Pcmod) from the hydraulic pressure generating source, the hydraulic controller for an automatic transmission supplies that first hydraulic pressure (for example, Pemod) to the second oil chamber to fix the first control valve.
Therefore, the hydraulic controller according to the present invention includes an oil passage which supplies the output of the switching valve to the second oil chamber of the first control valve. When the switching valve outputs the second hydraulic pressure from the first control valve, the hydraulic controller routes that second (adjusted) hydraulic pressure to the second oil chamber for feedback-control of the first control valve, and when the switching valve outputs the first hydraulic pressure of the hydraulic pressure generating source, the hydraulic controller routes that first hydraulic pressure of the hydraulic pressure generating source to the second oil chamber to fix the first control valve. Therefore, when the second hydraulic pressure output from the first control valve is used, a feedback-control is established, and when the first hydraulic pressure output from the first control valve is not used, the first control valve can be fixed. This prevents unnecessary oil drainage without adjusting the pressure of the first control valve, which results in a reduction of oil consumption in the hydraulic controller and in enhancement of fuel economy due to use of a smaller size oil pump and/or increased efficiency of the oil pump.
The hydraulic controller according to the present invention (for example, refer to FIG. 1) may be arranged so that the solenoid valve (SLT) outputs the signal pressure (Pslt) to a plurality of valves (for example, 77, 73). When the solenoid valve outputs the signal pressure to a plurality of valves, for example, when the first valve is not fixed, the first control valve simultaneously adjusts pressure to control the other valves. However, the first control valve can be fixed, which prevents unnecessary oil drainage without adjusting the pressure of the first control valve. This results in a reduction of oil consumption in the hydraulic controller and in enhancement of fuel economy due to capability of using an oil pump of reduced size and increased efficiency.
The hydraulic controller of the present invention in one preferred embodiment is applied to a continuously variable transmission which has a belt running around two pulleys. The effective diameter of at least one pulley is changed to change speed. In this embodiment the controller further includes a hydraulic servo which controls the effective diameter of a pulley responsive to receipt of a hydraulic pressure, and a second control valve which controls the hydraulic pressure supplied to the hydraulic servo, based on a signal pressure of a solenoid valve (SLT). Thus, the solenoid valve (SLT) outputs its signal pressure both to the first control valve and to the second control valve. When the first control valve is not fixed, it simultaneously executes a pressure adjustment when the torque capacity of the pulleys is controlled by the solenoid valve. However, the first control valve can be fixed, which prevents an unnecessary oil drainage without adjusting the pressure of the first control valve. This results in a reduction of an oil consumption in a hydraulic controller for an automatic transmission and enhancement of fuel economy due to a size-reduction in the oil pump and an increased efficiency of the oil pump.
A hydraulic controller according to the present invention may control engagement of friction engagement elements (C1, B1) at the time of starting, and include a pressure regulating valve which adjusts the hydraulic pressure of the hydraulic pressure generating source to a predetermined pressure (Pemod) and outputs it to the first control valve which, in turn, adjusts the hydraulic pressure (Pcmod) received from the pressure regulating valve (76) based on the signal pressure (Pslt) of the solenoid valve (SLT), and outputs it to the friction engagement elements (C1, B1) in starting. Once in motion (running state), a switching valve switches output to the friction engagement elements (C1, B1) from the pressure as adjusted by the first control valve to the hydraulic pressure (Pcmod) as adjusted by the pressure regulating valve. During running, when the first control valve is not fixed, it executes pressure adjustment. However, the first control valve can be fixed, which prevents an unnecessary oil drainage in the running state and results in reduction of an oil consumption and enhancement of fuel economy due to use of a smaller oil pump of increased efficiency.